Various types of spinal column disorders are known and include scoliosis (abnormal curvature of the spine), kyphosis (backward curvature of the spine), spondylolisthesis (forward displacement of a lumbar vertebra), and other disorders such as ruptured or slipped discs, broken or fractured vertebrae, and the like. Patients who suffer from such conditions usually experience extreme and debilitating pain. A technique known as spinal fixation, which results in the surgical/mechanical immobilization of areas of the spine and the eventual fusion of the treated vertebrae, has been used to treat such conditions and, in most cases, to bring to the patient a relief from pain. After the fusion of the vertebrae has occurred, the spinal fixation system is no longer required to immobilize the spinal region and could be removed if desired. However, it is preferable that the system is left in place, thus avoiding the necessity of subjecting the patient to a second surgery and to the possible complications associated with the surgery.
While it is preferable that the fixation system is left in place permanently, its presence can lead to the formation of a condition known as bursitis. Bursitis develops as the patient recovers from the surgical procedure of spinal fixation and resumes normal activities. The muscles of the back can rub over the nuts and clamps of the fixation system and become irritated. The muscles form a bursa or pad-like sac in response to the irritation, which may result in additional pain to the patient. To alleviate this pain, the patient is frequently subjected to additional surgery for the removal of the spinal fixation system.
It is desirable that a spinal fixation system is developed which, because it does not result in irritation of the back muscles, can be permanently left in place, thus avoiding the need to perform additional surgical procedures for the removal of the spinal fixation system. It is also desirable that the design of the system withstand lifelong implantation without requiring repairs or adjustments.